Spark responsive safety control system for gas burners



Feb. 17, 1953 R. SHOTTENFELD 2,628,676

SPARK RESPONSIVE SAFETY CONTROL SYSTEM FOR GAS BURNERS Filed Aug. 26,1950 INVENTOR ATTO R Y Patented Feb. 17, 1953 SPARK RESPONSIVE SAFETYCONTROL SYSTEM FOR GAS BURNERS Richard Shottenfeld, Jamaica, N. Y.,assignor to Ensign Ribbon Burners, Inc., Pelham Manor, N. Y., acorporation of New York Application August 26, 1950, Serial No. 181,6457 .2 Claims.

This invention relates to gas burners provided with ignition by electricspark for currently insuring ignition of the gas; more specifically thisrelates to safety devices for automatically shutting off the gas supplyto the burner when the ignition spark fails for example due to powerfailure. Normally the spark is produced by current from a so-calledignition transformer which delivers an alternating currentof high enoughvoltage to cause a spark to jump the air gap between a pair ofelectrodes as long as such current is being delivered to the electrodes.

According to one aspect, this invention relates to what may be termedinterrupted spark operation, namely a mode of operation in which thespark-producing current is interrupted rhythmically as by an interrupterfor the current that feeds the ignition transformer. In this way,- briefperiods during which the spark is alive alternate with similarly briefperiods during which the spark is dead. These periods will herein betermed the on-periods and the off-periods or the liveand thedead-periods of the spark. v

The purpose of interrupted spark operation is to reduce powerconsumption,.reduce wear of the electrodes, and to reduce the averageload on the transformer 50 that smaller electrical condoctors may beemployed. To be thus effective the lengths of the oiland on-periods areso proportioned that the off-period is too short to allow for the escapeof a dangerous amount of gas from the burner in the absence of a flame,while the on-period is long enough to provide a reasonable length oftime for ignition yet short enough to minimize, power consumption andload. To meet these requirements suitable proportions are of the orderof 3 seconds for the elf-periods and of the order of 3 seconds for theon-periods.

While a variety of automatic safety devices or safety control systems ingeneral are known for shutting off the gas in case of spark failure, aproblem lies in rendering such devices properly responsive where asystem of interrupted spark operation is employed. The problem lies indevising means for rendering vthe safety "device nonresponsive duringthe off-periods, but responsive to shut off the gas whenever the sparkremains off longer than the normal off-period provided for by theinterrupter.

Another problem lies in devising such a safety control system that willbe secure against rendering an erroneous or uncalled for response i caseof any fault within the system itself. That is to say, if any componentor element of the safety control system should fail, the response shouldinvariably be on the safe side, namely to shut off the gas.

It is among the objects of this invention to provide a safety controlsystem which is simple and inexpensive to manufacture, for preventinggas shut-off during the off-periods of the spark, yet to shut off thegas promptly when the spark remains off for a length of time appreciablyin excess of the normal off-period; to provide such a system thatis'fool proof in the sense that it is safe against rendering uncalledfor response in case a fault develops in the system, in other words toprovide a system in which any fault in thesystem itself willassuredly'cause the gas to be shut off; to provide such a system inwhich the spark must be restored manually as by push button operation;and to provide a system that is fool proof in regard to the push buttonoperation, in the sense that irrespective of the length of time the pushbutton is held pressed for opening the gas valve the closure of the gasvalve willnevertheless be assured when the spark is absent.

According to the invention these objects are attained by providing asystem in which an alternating current detector or monitor circuit isdependent upon and coupled through a step-down transformer, hereintermed the detector transformer, with the spark-producing high voltagecircuit. The term detector or monitor circuit is herein used to meanthat it is energized while the spark is functioning properly and is deadwhen the. sparkis dead. This detector circuit, according to theinvention, carries an alternating current which is rectified forenergizing the solenoid of a direct-current operated relay switch foropening and closing an independent energizing circuit foractivating asolenoid that opens and closes the gas supply valve for the burner inaccordance withthe opening and closing of the independent energizingcircuit.

Associated with the solenoid of the relay switch is a condenser sodimensioned as to store up, during each on-period of the spark,sufficient energy adapted in turn to discharge from the condenser masolenoid-energizing direction for holding the relay solenoid energizedand the relay switch closed during the off-periods of the spark, but

switch is provided and operable to close the detector circuit, and therelay switch comprises switch contacts which close when the relay switchis energized to close, so as to hold the detector circuit closed as longas the spark is operating normally although with the prescribedinterruptions.

A safety control system. embodying the invention comprises a primarypower supply circuit with interrupter; a high voltage spark-producingcircuit with spark electrodes for the gas burner and coupled through theignition transformer with the supply circuit; a detector circuit coupledthrough the detector transformer withthesparkproducing circuit, andhaving a rectifier in circuit with the solenoid of the relay switch. as"well as a condenser connected in parallel with the solenoid coil; and arelay controlled power supply for energizing the solenoid that operatesthe gas valve for the burner by the closing and opening of the. relayswitch of the detector circuit.

As this invention may be embodied in several forms withoutdeparting-fromthe spirit or essential characteristics thereof, the present embodimentis therefore illustrative and not restrictive, since the scope of theinvention is defined by the appended claims rather than by thedescription preceding. them, and all changes that fall within the metesand bounds of the. claims are-therefore intended to be embracedby thoseclaims.

The drawing figure shows the. burner with solenoid-actuated gas. supplyvalvediagrammatically, as wellas an associatedlwiring. diagram embodyingthe invention.

A tube-shaped gas burner. I0. is. indicated by a burner tube having alongitudinal gas port l2 producing a ribbon-like flame when theburner islit. The burner tube. is. closed atone end l3 and is supplied with. gas.at. the other end from a gas nozzle. I4: surrounded. by an annularpassage |5 through. which. the gas jet from. the nozzle draws combustionair. Associated with the burner is a pair of spark electrodes E1 and E2presenting. between them a spark gap G.

The gas supply to the nozzle I4 is by way of a solenoid-controlled valve|5 provided in a gas supply pipe l6 having a hand-operated. mainshut-off valve H. An electromagnetically operated mechanism, for examplesolenoid. l8 for opening and closing valve l5 comprises an armature |8and a solenoid. coil l9 having terminals I 9 and la the armatureengaging a. valve-actuating arm 28. The valve. I5 is held closed by aspring 2| acting upon the. armature in a valve closing. direction whenthe solenoid coil. I8 is deenergized, while energization of the solenoidcoil IE will pull the armature upwardly against the tension of spring 2|to open the valve and to keep it open as long as the solenoid coilremains energized- The system is supplied with operating current fromsupply lines 22 and 23 furnishing, a suitable alternating current, forexample of 110 volts. In terms of a general outline the system forproducing the control effects comprises a primary power supply circuit24 with an interrupter 25, a spark-producing circuit 26 with electrodesE1 and E2 and supplied from circuit 24 through a step-up transformer 21herein termed the ignition transformer having a step-up ratio of theorder of 110 volts to about 5000 volts for Jumping the spark gap G; adetector circuit 28 coupled with the spark producing circuit 26 througha step-down transformer 2!! herein termed the detector transformer, thiscircuit having a rectifier 38 in circuit with the solenoid coil 3| of arelay switch 32, and a condenser 33 connected across the solenoid coil3|, which detector circuit may be closed by a starting switch shown inthe form of a push button 34 adapted to close and open a pair ofcontacts 88 and 82, which starting switch is in. parallel with a. pairof. contacts 35 and 36 adapted'tobe closed and to be held closed byrelay switch 32; and a relay-controlled supply circuit 31 for energizingsolenoid H! which circuit is adapted to be closed and to be held closedby the relay switch 32 closing a pair of contacts 38 and 38. When thespark across gap G functions normally although. rhythmicallyinterrupted, the relay switch 32. will; be held closed so that solenoidcoil. I8 is energized without interruption and armature l8 heldconstantly in valve-closing position.

The relay switch 32 comprises an armature 48 actuated'by the solenoidcoil 3| and has a pair of switch. members 4|. and 42 whereby itsimultaneously'closes. and openscontacts, 35 and 36 as Well as.contacts. 38 and 39. A. spring 43 acting upon armature 40 holds thesecontacts open when coil. 3| is de-energized'.

The interrupter 25 comprises a pair of contacts 44 and 45, contact 44stationary and contact 45 movable. These contacts. are rhythmicallyopened and closedby a rotary cam member 46 engaging, the movable.contact. 45, the cam member 46. being. rotated as by a motor 41 suppliedwith current through. conductors 48 and 49 leading. to points5|i and.5|. respectively on supply lines 22 and 23.

Now follows a more detailed description of th safety control. system in.terms. of the circuits just. outlined. namely the. primary power supplycircuit 24., the sparks-producing circuit 26, the detector circuit 38.and the relay-controlled power supply circuit 31.

The primary power supply circuit, 24 comprises a conductor 52 leadingfrom a point 53 on power line 22 to a terminal 54 of a primarytransformer coil 55' of the ignition transformer 21, a conductor 58leading from a terminal 51 of transformer coil 55 to movable interruptercontact 45, a conductor 58 leading from stationary interrupter contact44 to a point 59 on power line 23.

The spark-producing circuit 26 comprises a conductor 68. leading from aterminal 6| of secondary coil 62 of ignition transformer 21 to sparkelectrode E1; a conductor 63 leading from spark electrode E2 to aterminal 64 of primary coil 65 of detector transformer 28; a conductor66 leading from a terminal 61 to a terminal 68 of secondary coil 62 ofignition transformer 21, conductor 68 being grounded as at 68. Thecharacteristics of the ignition transformer 21 are such that when aspark is maintained across gap G then the spark producing circuit 26operates substantially as a constant current circuit in which variationsof impedance do not effect appreciable changes in the magnitude oi thespark producing current. Therefore the term ignition transformer hereinconnotes a transformer having the characteristics just defined.

The detector circuit 28 comprises a conductor 10 leading from a terminal1| of secondary coil 12 of detector transformer 29 to a terminal 13 ofrectifier 38 which may be in the nature of a selenium rectifier; aconductor 14 leading from a terminal 15 of the rectifier by way of point16 to a terminal 11 of relay solenoid coil 3 I; a conductor 18 leadingfrom a terminal 19 of solenoid coil 3| to a contact of push buttonswitch 34; a

conductor 8| leading from a contact 82 of the push button switch by wayof point 83 to a terminal 84 of secondary coil 12 of detectortransformer 29, a conductor 85 leading from point 19 to relay switchcontact 36 and a conductor 86 leading from relay switch contact 35 topoint 83, so that relay switch contacts 35 and 36 can be closed inparallel with push button contacts 80 and 82; a conductor 81 leadingfrom point 19 to a terminal 88 of condenser 33 and a conductor 89leading from a terminal 90 of the condenser to point 16.

Th relay-controlled power supply circuit 31 comprises a conductor 8|leading from a point 92 on power line 22 to relay switch contact 39; aconductor 93 leading from relay switch contact 38 to terminal I9 ofsolenoid coil l9; and a conductor 94 leading from terminal Ill ofsolenoid coil l9 to a point 95 on power line 23. A signal light 98connected across solenoid coil I3 is lit to indicate the gas valve beingopen with spark operation being in order, the light being extinguishedwhen due to failure of the spark to operate normally or due to any faultin thesystem the solenoid I9 is de-energized and the gas valve I isshut.

Operation In order to start the burner as well as the spark, with themain gas valve I! open, the 110 volt power from lines 22 and 23 is fedto the ignition transformer 21 by way of interrupter 25 so that a sparkwill appear across gap G between electrodes E1 and E2 at rhythmicintervals. For example the function of the interrupter 25 may be such asto produce alternating onand offperiods of the spark with on-periods ofabout 3 seconds and off-periods of about 3 seconds duration.

The spark-producing current derived from the ignition transformer 2'!energizes the primary coil of detector transformer 29, while thedetector circuit 28 is open due to the then open condition of relayswitch 32 and the open condition of push button switch 34, 88, 82. Thispush button switch represents a switch device for holding a pair ofcontacts normally open and for momentarily closing them through manualoperation. Hence, even though the spark is functioning in its normalrhythmically interrupted manner, the gas valve I5 still remains closedbecause of the then tie-energized condition of solenoid coil I9, asindicated by the full-line closed position of valve lever 20 thus heldby spring 2|.

In order to light the burner the operator must press the push button 34normally held open by a spring, to effect the closing of contacts 88 and82 to establish the detector circuit 28 from contact 82 throughconductortl, secondary coil E2 of detector transformer 29, conductor 10,rectifier 30, conductor 14, relay solenoid coil 3|, point 19, andconductor 18 to terminal 8|).

The closing of push button switch 34, 80, 02 energizes relay solenoidcoil 3| pulling in the armature 48 against the tension of the spring 43,thereby closing switch member 4| upon contacts 35 and 36 and switchmember 42 upon contacts 38 and 39. Push button 34 may then be releasedas relay coil 3| remains energized by reason of the closing of contacts35 and 36, while simultaneously solenoid coil I9 is energized by theclosing of contacts 38 and 39, and draws in o r'pullsup the armature 18*against tension of spring 2|, thus opening the gas valve l5 as isindicated by the dot-and-dash line position of the valve actuating leverML The condenser 38 connected across the relay solenoid coil 3| isprovided to store up energy while the relay solenoid vcoil is energized,and to discharge the stored up energy in a, coil-energizing direction soas to continue the energization of coil 3| even after current in thedetector circuit proper will have ceased to flow during the ofi-periodof the spark when the spark producing circuit 26 as well as the powersupply circuit 24 is dead. The capacity of the condenser is sodimensioned as to store during a singl on-period and to discharge durina single off-period sufficient energy for holding relay solenoid coil 3!energized and relay switch 32 closed until another on-period of thespark will have started due to the closing of interrupter contacts 44and 45. In this way, even though the spark is operated with rhythmicinterruptions, the gas valve I5 will nevertheless remain opencontinuously that is through the on-periods as well as the off-periodsof the spark. I

Yet, the capacity of condenser 33 is so dimensioned that it requiresonly a moderate extension of the off-period of the spark to allow therelay solenoid coil 3| to become de-energized allowing spring 43 to openthe relay switch 32 and thereby to open both the detector circuit 28 aswell as the power supply circuit 31, thereby de-ener gizing the solenoidcoil l8 and allowing spring 2| to close the gas valve I5 Thus, if theoilperiod of the spark is unduly extended, the gas valve will shut andwill not open again irrespective of whether or not normal operation ofthe spark is re-established. However, if such normal spark operation hasbecome re-established, it is necessary to initiate the opening of thegas valve again by pressing the push button 34.

While the embodiment so far described requires manual operation as ofthe push button switch [34 to reestablish the spark and to re-light thegas burner once the gas valve has been shut, for instance when the powersupply has failed, it may be desired to have the spark restoredautomatically to re-open the gas valve directly when the power supply isrestored. To this end there is shown a switch 91 which may be closed tobridge the normally open push button switch contacts 80 and 82. Withswitch 9'! closed the restoration of the power supply from lines 22 and23 will at once restore the spark operation. energize relay solenoido3l,and thus close relay switch 32 causing solenoid l9 to be re-energizedand thus gas valve |5 to be opened.

Since it is one of the features of this invention that the system isfool proof against rendering false control effects with respect to thegas valve irrespective of any fault that may develop within the systemitself, there will now be presented a discussion of possible break-downsor faults in the system along with reasons why such breakdowns or faultswill in any instance assure the automatic closing of the gas valveirrespective of whether the starting push button switch 34 is being heldclosed.

Such possible break-down or faults are present (a) If the primary coil55 of ignition transformer 21 be open; then no energy enters thesecondary coil 62, and the system is dead causing gas valve l5 to beclosed by spring 2|.

(1)) If the primary coil 55 be shorted, then the effect is the same asin (a). k

(c) If the secondary coil 62 0f ignition transformer 21 be open, then nocurrent is supplied to primary coil 55 of detector transformer 29, and

a'eaaevs relay circuit through secondary 'coil 12 is dead, allowingrelay switch, 32 to be opened by spring 43, thus causing gas valve I toclose.

(d) If the high tension conductor 60 leading to the spark electrode E;be grounded, then there is no spark at the gap G and no current inconductor 63 and coil 65 of detector transformer 29, so that the systembeyond the spark producing circuit 26 is dead causing gas valve l5 toclose.

(e) If low tension conductor 63 be grounded, then whether or not a sparkexists across spark gap G, the detector transformer 29 will neverthelesssubsequently remain de-energized causing gas valve If: to be closed byspring 2|.

(f) If primary coil 65 of detector transformer 29 be shorted, then theeffect is the same as in (e) when conductor 63 is grounded.

(g) If conductor 60 or 63 or transformer coil 65 or conductor 66 beopen, or if the spark gap G becomes too wide to allow a spark to jump,then the detector transformer 29 will be de-energized, causing the gasvalve l5 to be closed by spring 2|.

(It) If any one of the elements of relay circuit 28 (that is transformercoil 12, conductor 13, rectifier 30, conductor 14, solenoid coil 3|,conductor 13, contacts 80 and 82, or conductor 8|) be open, then relaysolenoid 3| receives no current, the relay switch 32 opens, andconsequently the gas valve I5 is shut by spring 2|.

(1) If secondary coil '12 of detector transformer 29 be shorted, noenergy is delivered to the de tector circuit 28, so the relay solenoid3| is deenergized causing as valve l5 to be closed by spring 2|.

(7') If rectifier 30 be shorted, then alternating current is impressedacross condenser 33 in parallel with relay solenoid coil 3|, butsolenoid coil 3| being built for direct current operation does notrespond to alternating current, and condenser 33 now represents ineffect a short circuit across solenoid coil 3| for this impressedalternating current, so that solenoid coil 3| remains de-energizedcausing gas valve I5 to be closed by spring 2|.

(k) If condenser 33 be short-circuited, then the relay solenoid 3|receives no energy, causing spring 43 to open relay contacts 35 and 36,and gas valve l5 to be closed by spring 2|. No damage can result to thesystem, as a result of operation with shorted condenser 33, since thevery shorting of the condenser acts to choke off any supply of energyfrom detector transformer 29. In other words, with a shorted condenser33 the rectifier 30 being placed directly as an excessive load acrosstransformer coil 12 has the effect of lowering the impedance of primarycoil 65 so that less energy is abstracted from the spark pro ducingcircuit 26, since the spark producing current in that circuit ismaintained substantially constant by virtue of the characteristics ofignition transformer 21.

i Z) If condenser 33 be open, then relay solenoid coil 3| receivespulsating direct current in the form of half-wave impulses, which isinsufficient and ineffective for keeping relay contacts 35, 30 and 38and 39 closed, thus causing gas valve l5" to be closed by spring 2|.

(m) Or if any one or more of the foregoing faults occur, then the gasvalve IE will be closed due to de-energization of relay solenoid coil3|.

(a) If relay solenoid 3| be shorted or open, then relay contacts 35, 36and 38, 39 will remain open, causing gas valve l5 to be closed by spring2|.

ground.

What I claim is:

1. In combination with a gas burner having a gas valve operable to openand close the gas supply to the burner, a pair of ignition sparkelectrodes, a solenoid coil controlled armature for'so operating thevalve, 2. power supply circuit for controlling the solenoid coil, astep-up ignition transiormer the secondary coil of which suppliesalternating current to the spark electrodes for sustaining a sparkpassing between the electrodes, current interrupting means forintermittently supplying current to the primary coil of the ignitiontransformer whereby spark onperiods of a controlled length alternatewith spark off-periods of a controlled length; a safety control systemfor shutting the gas valve when the spark fails for a length of timeappreciably in excess of the length of its off-period, which systemcomprises a step-down detector transformer having a primary coil incircuit with the secondary coil of the ignition transformer as well asin circuit with said electrodes to constitute a spark circuit, adetector circuit comprising the secondary coil of said detectortransformer, a rectifier, a relay solenoid coil and a starting switch, acondenser connected in parallel with said relay solenoid coil, a currentholding connection including a pair of switch contacts in parallel withsaid starting switch and adapted to be opened or closed, an armaturecontrolled by said relay solenoid coil to close said current holdingswitch contacts when the solenoid is energised and to open said currentholding switch contacts when the solenoid is de-energized, a second pairof switch contacts disposed to be closed and opened by said lastmentioned armature for thereby closing and opening said power supplycircuit concurrently with the closing and the opening respectively ofsaid current holding switch contacts, said condenser being dimensionedand adapted to receive a charge of enerry by said rectified currentduring the on-period of the spark, which energy is adapted to dischargethrough the relay solenoid coil in a solenoid energizing direction andis sufficiently large and effective to hold both said pairs of contactsclosed at least until a subsequent on-period of the spark has startedand is insufliciently large to keep the solenoid energized appreciablylonger than the length of the off-period of the spark, so that said whenthe spark remains off for a length of time appreciably in excess of thelength of the 01L period of the spark.

2. The combination according to claim 1, with the addition of a groundconnection in the spark circuit, said ground connection being disposeddirectly between the secondary coil of the ignition transformer and theprimary coil of the detector transformer whereby the primary of thedetector transformer is placed at low potential to RICHARD SHOTTENFELD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,154,041 Gille Apr. 11, 19392,209,410 Lowrey July 30, 1940 2,506,913 Baker May 9, 1950

